There's no doubt that HDR is a popular form of photography (I did a bit of a how-to, if you're not familiar with it), but mostly, I can't help but thinking that it's a bit of a specialist field.

Until, that is, I started using it on my iPhone. Most of the time, I don't need it; but the other day, I wanted to take a photo of a piece of graffiti. If I were photographing this properly, I'd have brought a SLR, and waited for the sun to go away so I could get even lighting across the whole image, but in this case, it was only going to be a quick snapshot.

I did my usual thing when I take photos with my iPhone:

Point

Shoot

Done

So, as you can see, it's a graffiti piece of God on a Sea-Doo. I thought it was pretty funny (those Porteños - that's people from Buenos Aires - really have a quirky sense of humour), but part of the image was missing.

The problem was that the direct sunlight was washing out the highlights on the far right, but the foreground was correctly exposed.I also tried exposing for the highlights (by pressing my iPhone's screen on the far right side, on the sphinx), but no avail: doing that plunged my right-hand side into deep darkness.

This is a great example of how limited dynamic range can make a photograph impossible: It is either too light, or too dark, and there's nothing you can do about it: You've hit the limits of the imaging sensor.

Or have you?

High Dynamic Range to the rescue

So, by using HDR processing, the iPhone takes two photos quickly after each other, and uses a HDR algorithm to use the dark bits from the light image, and the light bits from the dark image, to ensure you get an even exposure. In effect, you're cramming in a load of extra information - much more than the sensor is really able to capture in one exposure - into a single frame.

The result is nothing short of pure magic.

For the sake of comparison, let me post them both underneath each other here:

Non-HDR

HDR

Astonishing, eh? Now, we have detail both in the highlights AND in the shadows. Of course, it still isn't a masterpiece - it's still, unmistakably, a snapshot - but it's a technically much better snapshot than the first one.